1. Field of the Invention
This invention relates to automatic washing machines and, more particularly, to automatic washing machines that have a system for controlling the temperature of fill water introduced into the washer tub.
2. Description of the Prior Art
Systems for providing selectable water fill temperatures in clothes washers are well known. For example, sophisticated and expensive systems employing temperature sensors and microprocessor controls have been employed. U.S. Pat. Nos. 4,330,081, 4,406,401, 4,528,709 and 4,643,350 all disclose water temperature control systems for automatic washers utilizing costly microprocessor controls for storing and processing temperature data for achieving desired fill temperatures. These systems all have the disadvantage of being relatively costly and relatively complicated.
More economical systems that merely turn on one or both water valves to achieve hot, cold or warm have also been employed. U.S. Pat. No. 4,147,297 discloses a temperature sensing system which utilizes electro-mechanical means but is only responsive to the incoming hot water supply. No temperature sensing means for the incoming mixed hot and cold water is provided.
There is, therefore, a need for an accurate, low cost apparatus and method for controlling fill water temperatures responsive to the temperature of the combined incoming supply of water from a hot water inlet valve and a cold water inlet valve. Furthermore, there is a need for a relatively low cost improved water temperature control apparatus and method responsive to the temperature of the combined supply of hot and cold water, which apparatus and method can control the operation of the hot water inlet valve and cold water inlet valve such that the combined supply of water flowing into the wash bath will always be maintained below a preselected one of two alternate predetermined temperature levels.